Lipoprotein metabolism in normal human liver, the livers of patients with hereditary hyperlipidemias, and certain human hepatoma lines is being studied in serum-free culture systems. Work previously initiated with liposome interaction with melanoma cells has been expanded because of interesting information about non-specific lipid uptake and, in particular, lipid vesicle uptake by tumor cells. Careful categorization of in vitro responses has been extrapolated to in vivo systems for the first time. Several parameters which make liposomes theoretically practical in limited situations are being elucidated.